The 2004 sci-fi movie blockbuster The Day After Tomorrow depicted a global-warming scenario that seemed too weird to be plausible.

The North Atlantic Ocean circulation became disrupted, causing the northern section of North America and Europe to experience a sudden ice age.

As that occurred, a tsunami flooded Manhattan and massive storms pounded Tokyo and Los Angeles. It was a disaster of epic proportions, which took place within a couple of hours of screen time.

Climate scientists, including Andrew Weaver, then at the University of Victoria, pooh-poohed the possibility of a new ice age.

And Stefan Rahmstorf of the Potsdam Institute for Climate Research declared that the scenario was "unrealistic and exaggerated".

However, Rahmstorf also stated that some of the dialogue introduced audiences to key ideas about the risk of a shutdown of the North Atlantic Ocean current.

Flashforward 11 years and researchers at the Potsdam Institute, including Rahmstorf, are offering up a frightening real-life development, which was published this week in the journal Nature.

In the video below, the Potsdam Institute's Levke Caesar explains that the Gulf Stream is one of Earth's major ocean-circulation systems, redistributing heat on the planet.

She's the lead author of a new study reporting that that a "sea-surface fingerprint" shows that it has slowed by about 15 percent since the middle of the 20th century.

Video of Stronger evidence for a weaker Atlantic overturning

Watch a short video explaining the significance of the slowdown of the Gulf Stream.

According to Caesar, this fingerprint shows cooling south of Greenland and warmer waters off the east coast of the United States.

She says the "main reason" is rising greenhouse gas emissions.

In the same video, Rahmstorf says that climate models predict a "very specific pattern" of sea surface changes when the Gulf Stream system slows down.

He says that "exactly that pattern" has been in observational data since about 1870 in the Gulf Stream.

"I see no other explanation for this than indeed a slowdown of the Gulf Stream system," Rahmstorf adds. "That would have major implications for people living on both sides of the Atlantic.

"For example, this slowdown leads to excessive sea-level rise on the east coast of the United States," he continues. "It changes the tracks of the storms going into Europe and it has even been linked to extreme heat waves in Europe."

Caesar says as greehouse gas levels rise, this brings more precipitation, as well as the loss of sea ice in the Arctic and melting of glaciers on Greenland.

This adds fresh water to the North Atlantic.

In the past, the Gulf Stream brought warm water north. As it cooled, it became more dense, causing it to sink.

The colder, denser water then flowed south in the opposite direction below the warmer water going north in the current.

But the new fresh water being dumped into the North Atlantic is hinderng the engine driving the Gulf Stream.

That's because precipitation and melted ice is less dense, and doesn't sink so easily.

This accounts for the slowdown. And if human beings don't curb the release of greenhouse gases into the atmosphere, it's only going to get worse.

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